1. Field of the Invention
The invention relates to a process for the simultaneous cleaning of both seat surfaces of a double seat valve that is in contact with product on at least one side. The process is particularly suited for use in the food processing industry. The process involves supplying cleaning and/or disinfecting agents to a given double seat valve to clean it. The valve is equipped with two closing elements that are movable independently and relative to each other. The closing elements are moved from the closed position into an open position by activating mechanisms. At least one closing element is piston like and can be moved within a cylinder bore-hole connecting the two valve casings while providing a radial seal. The closing elements enclose between them a leakage cavity, in the closed as well as in the open position. The leakage cavity opens outside the valve through a borehole within the valve stem of the lower closing element leading from the valve casing in a downward direction.
2. Discussion of Related Art
In the known double seat valves, only the cleaning of the seat surfaces of the lower closing element is possible, as in German Pat. No. 24 56 675, or the cleaning of both seat surfaces is possible, but only at different times, as in German Utility Pat. No. 80 03 805, that is, the cleaning of the seat surface of the closing element in contact with the product cannot be performed at the same time as the cleaning of the seat surface of the other closing element while the product is present. The product is always present, for example, in the case of container stop valves, if they are designed as double seat valves. In these valves, the valve casing on the container side as well as its closing element is continually in contact with the product, while the other valve casing, which is a part of the piping, is cleaned by flushing it at more or less regular intervals. In the case of the aforementioned known double seat valves, the closing element blocking the piping being cleaned is partially raised by an activating device that is independent of the main drive, so that the seat surface corresponding to this closing element is cleaned,. In this operation, the cleaning agent enters the leakage cavity between the closing elements through a gap between a closing element and its seating surface. From there the cleaning agent is discharged outside the valve through a borehole within the valve stem of the lower closing element which points downward, out of the valve casing.